Tests involving children as young as three months suggest biological differences and not social pressures dictate which toys children like to play with.
The U.S. study looked at babies aged three to eight months - before they can identify even the gender of other people.

Researchers placed a doll and truck inside a puppet-theatre style box and showed them to 30 children - 17 boys and 13 girls - for two ten-second intervals.The findings, from researchers at Texas A&amp;M University, overturn conventional wisdom that children's toy preferences are down to social conditioning.

The study reinforces the findings of previous research by Dr Alexander involving green vervet monkeys. Male monkeys spent more time playing with traditional male toys such as a car and a ball than did female monkeys. The female monkeys, however, spent more time playing with a doll and a pot than did the males.&nbsp;

These resources for learning about genetics by the University of Utah's Genetic Science Learning Center include interactive visualizations, 3D animations and activities. Student activities include taking a "tour" of DNA, a chromosome or a protein, building a DNA molecule, or exploring the inside of a cell.
The university is also building a sister site, Teach.Genetics, with print-and-go lesson plans and supplemental materials for some channels on the Learn.Genetics site.